Development of an interface device combining a projector with a camera has been under way in recent years. Such an interface device provides an interactive operation by recognizing a manipulation content on image data captured by a camera, the manipulation being performed on an image projected from a projector. Each of PTLs 1 and 2 discloses an interface device combining a projector with a camera.
The interface device in PTL 2 includes an irradiation means using a phase modulation type spatial modulation element. A projector using a phase modulation type spatial modulation element is able to display a desired target image on a projection surface by displaying a phase distribution for projecting the target image on a display surface of the spatial modulation element and projecting reflected light of light irradiated on the display surface. The interface device in PTL 2 forms a phase distribution displayed on the spatial modulation element one by one, by using an optimization method such as an iterative Fourier transform method. The iterative Fourier transform method iterates processing any number of times until an operation result converges, resulting in a high calculation cost. Accordingly, when a high-quality target image is displayed in real time, an amount of calculation may become enormous, causing a delay in the processing.
PTL 3 discloses a method for shortening a calculation time, when a computer generated hologram by using an optimization method such as the iterative Fourier transform method.
At first, the method in PTL 3 generates a sub-target reconstructed image including part of pixels of a target reconstructed image and generates a computer-generated hologram for reconstructing the sub-target reconstructed image. Next, the method in PTL 3 generates a new sub-target reconstructed image with increased resolution, being obtained by adding pixels to the already-generated sub-target reconstructed image. Then, the method generates a computer generated hologram for generating the new sub-target reconstructed image. The method in PTL 3 repeats generation of a new sub-target reconstructed image and generation of a computer-generated hologram for generating the sub-target reconstructed image until the computer-generated hologram reaches a target number of pixels.